The long-term research goal is to determine the mechanism of action of androgens on pituitary gonadotropin secretion in vitro. The inherent activity of the ten natural androgens on LH and FSH release by pituitary culture systems is to be studied in such a way as to definitively test the hypothesis that the dose duration, and form of androgen are important variables influencing gonadotropin release. The effects of aromatizable androgens (e.g., testosterone and androstenedione) will be compared to those of non-aromatizable androgens (e.g., dihydrotestosterone) and estradiol. The amount of androgen interconversion and metabolism to estrogen will be quantitated by double isotope techniques. Rat pituitary organ culture will be used to determine how short-term androgen estradiol exposure effects gonadotropin release and whether the sex hormone status of the pituitary donor qualitatively influences these androgen or estrogen effects. The steroids will be added to the culture system for the shortest effective time interval in order to minimize the amount of androgen interconversion and metabolism. Pituitary cell culture techniques will be used to determine whether the response to short-term androgen exposure is the same in pituitary cell culture as in pituitary organ culture and to determine the effects of long-term androgen exposure. The interactions of selected androgens with estrogen, progesterone, and 17-hydroxyprogesterone will also be determined. Androgen effects will be quantitated in terms of LH and FSH secretion into the culture medium as determined by radioimmunoassay. Multiple parameters of gonadotropin release will be evaluated: basal LH and FSH, gonadotropin releasing hormone (GNRH)-stimulated LH and FSH levels, and the sensitivity of LH and FSH secretion to GNRH. The results will be interpreted in the light of the amount of androgen metabolism in the culture systems.